1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a printer, a facsimile apparatus, or a multifunction apparatus, configured to form an image electrophotographically.
2. Description of the Related Art
In an image forming apparatus employing an electrophotographic image forming process, an image is formed on a recording material, such as a sheet, in the following manner. First, an electrostatic latent image is formed on a photosensitive member as an image carrying member. The latent image is developed with developer and is thus visualized into a toner image. The toner image is transferred to the recording material at a transfer nip formed between the photosensitive member and a transfer member. The recording material having the toner image transferred thereto is nipped at and is conveyed through a fixing nip formed between a fixing roller and a pressure roller that are included in a fixing device, whereby the toner image is thermally fixed on the recording material. Thus, an image is formed on the recording material.
The transfer member is urged toward the photosensitive member by an urging member such that the transfer nip is formed between the transfer member and the photosensitive member. Therefore, the transfer member is in pressure contact with the photosensitive member. For example, with the photosensitive member and the transfer member being in pressure contact with each other, the image forming apparatus may be transported. In such a case, if the image forming apparatus is transported over a long time, the transfer member may be deformed or rubbed against the photosensitive member, or softener, cross-linker, or the like that has bled from the transfer member may adhere to the photosensitive member.
Japanese Patent Laid-Open No. 2010-262215 discloses an image forming apparatus in which, when helical gears provided at two respective axial ends of a photosensitive member are in mesh with helical gears provided at two respective axial ends of a transfer member, the photosensitive member and the transfer member are separated from each other. The image forming apparatus disclosed by Japanese Patent Laid-Open No. 2010-262215 is transportable with the transfer member being separated from the photosensitive member by the helical gears. Furthermore, when an image is to be formed, the helical gears at the two ends of the transfer member slide, whereby the helical gears on the transfer member are disengaged from the helical gears on the photosensitive member. At the disengagement of the helical gears, the transfer member comes into pressure contact with the photosensitive member.
In the apparatus disclosed by Japanese Patent Laid-Open No. 2010-262215, however, the helical gears provided at the two ends of the transfer member need to be moved individually. Therefore, it is difficult to assuredly bring the transfer member into contact with the photosensitive member.
Furthermore, in the apparatus disclosed by Japanese Patent Laid-Open No. 2010-262215, even if the transfer member is in pressure contact with the photosensitive member, the axial ends of the transfer member are constantly urged toward the inner side in the axial direction by the helical gears. Therefore, the transfer member is subject to an urging force even in the state of being in pressure contact with the photosensitive member. Consequently, the rotation of the transfer member may become unstable.